You can evangelize straight from your Old Testament, what the Jews call the Tanakh.
The Son of God is mentioned in many, many places, his life, his death, his resurrection, his ascenstion to the right hand of God Almighty, are all in the Old Testament
Proverbs 30:4: The Son's name?
Isaiah 9:6; 53: The Son is born and his name is Almighty God, and he must die for the people
Daniel 7: the Son's ascension to the Father's Throne